This application claims the priority of Japanese Application No. 2001-314967, filed in Japan on Oct. 12, 2001, the disclosure of which is expressly incorporated by reference herein.
1. Field of the Invention
The present invention relates to multi-row rolling mills, methods of operating these mills, and rolling equipment that uses the mills.
2. Description of Prior Art
Hot coils, the materials to be cold-rolled, are produced using hot-rolling equipment. Under prior art, slabs 200 mm or more in thickness are cast by a continuous casting machine and these slabs are then provided with unidirectional or reversing-type rolling by a plurality of pre-rolling mills to form bar materials. After these bar materials have been further rolled to the required thickness by a tandem rolling mill group consisting of a plurality of continuously arranged rolling mills, the bar materials are cooled by a cooling apparatus and wound by a coiler to form the hot coils mentioned above. Such hot-rolling equipment intended for mass production is very large in scale.
In recent years, importance has been attached to the recycling of iron scraps, coupled with the occurrence thereof in great quantities, and the tendency for distributed arrangement of small-scale small-volume production equipment, rather than integrated installation of large-scale large-volume production equipment, has been increasing. This tendency has resulted in construction of so-called “mini-hot” systems, namely, hot-rolling equipment up to about one million tons per annum in terms of hot-coil production scale. With reference to the production capabilities of cold-rolling equipment, on the other hand, tandem rolling equipment with a continuous arrangement of four to five rolling mills is up to about 1.5 million tons per annum in production volume, and the maximum production volume by single-stand reversing cold-rolling mills ranges from about 0.3 to 0.5 million tons per annum. For cold-rolling equipment connected to small-scale small-volume production equipment called the “mini-hot”, it is appropriate to have a production scale up to one million tons per annum. An example of an equivalent to such equipment is the twin-stand tandem reversing mill described on page 144 of STEEL TIMES APRIL 2000 (hereinafter, this mill is referred to as the twin-stand reversing mill).
As set forth in Japanese Patent Application Laid-Open Publication No. Hei 9-239413, rolling equipment having at least two groups of rolls in one pair of housings, designed so as to enable rolling to be repeated at least twice during one path, and capable of achieving a production scale up to one million tons per annum by creating a high-pressure atmosphere within a short time by use of a single-stand reversing mill (hereinafter, such equipment is referred to as the twin-reversing mill), has also become available.